[Federal Register Volume 68, Number 86 (Monday, May 5, 2003)]
[Proposed Rules]
[Pages 23673-23677]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-10269]


-----------------------------------------------------------------------

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 146

[FRL-7488-8]


Underground Injection Control Program--Relative Risk Assessment 
of Management Options for Treated Wastewater in South Florida; Notice 
of Availability

AGENCY: Environmental Protection Agency.

ACTION: Notice of availability.

-----------------------------------------------------------------------

SUMMARY: On July 7, 2000, the Environmental Protection Agency (EPA)

[[Page 23674]]

proposed revisions to the Underground Injection Control (UIC) 
regulations that would allow for continued wastewater injection by 
existing Class I municipal wells that have caused or may cause the 
movement of fluid into or between underground sources of drinking water 
(USDWs) in specific areas of South Florida. These revisions would 
provide owners and operators of such wells with an alternative for 
compliance with the existing UIC regulations, which prohibit such fluid 
movement, by allowing them to continue using their wells provided the 
injection does not endanger USDWs. Also in 2000, in a separate but 
related initiative, Congress directed EPA to conduct a relative risk 
assessment of four management options for treated municipal wastewater 
in South Florida: deep (Class I municipal) well injection, ocean 
disposal, surface discharge, and aquifer recharge. This document 
announces the availability of the relative risk assessment report 
required by Congress. EPA will consider the information collected on 
deep (Class I municipal) well injection contained in this relative risk 
assessment in making a final determination on the July 7, 2000, 
proposed rule. In a separate document in today's Federal Register, EPA 
is soliciting public comment on how this information in the relative 
risk assessment should inform the final rule on deep municipal 
wastewater injection in South Florida.

DATES: Comments on this notice of the data availability must be in 
writing and either postmarked or received by the docket by July 7, 
2003.

ADDRESSES: Send written comments to: Nancy H. Marsh, U.S. Environmental 
Protection Agency, Region 4, 61 Forsyth Street, SW., Atlanta, GA 30303-
8960. Comments must be submitted electronically to [email protected]. 
For additional information see Additional Docket Information in the 
SUPPLEMENTARY INFORMATION section of this Federal Register document.

FOR FURTHER INFORMATION CONTACT: For inquiries, and/or to access the 
risk assessment report, contact Nancy H. Marsh, Ground Water & UIC 
Section, EPA Region 4, 61 Forsyth Street, SW, Atlanta, GA 30303 (phone: 
404-562-9450; E-mail: [email protected]) or Howard Beard, Office of 
Ground Water and Drinking Water, U.S. Environmental Protection Agency, 
EPA East, 1200 Pennsylvania Ave., NW., Mail Code 4606M, Washington, DC 
20460 (phone: 202-564-3874; E-mail: [email protected]) or contact 
the Safe Drinking Water Hotline, phone 800-426-4791. The Safe Drinking 
Water Hotline is open Monday through Friday, excluding Federal 
holidays, from 9 a.m. to 5:30 p.m. Eastern daylight-saving time.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. General Information
    Who Are Regulated/Affected Entities?
II. Background
    A. Definition of Class I Municipal Wells
    B. Proposed Rule for Class I Municipal Wells in Florida
    C. Relative Risk Assessment of Management Options for Treated 
Municipal Wastewater in South Florida
III. Findings of the Relative Risk Assessment
    A. What Level of Treatment and Disinfection Is Provided?
    1. Deep Well Injection
    2. Ocean Disposal
    3. Aquifer Recharge
    4. Surface Discharge
    B. What Stressors Remain (After Treatment) That May Be a 
Concern?
    C. What Exposure Pathways Are (or May Be) of Significance?
    D. What Is the Overall Estimate of Risk?
    1. Human Health
    2. Ecological Health
    E. What Are the Important Data or Knowledge Gaps?

I. General Information

Who Are Regulated/Affected Entities?

    This notice is limited in application to the owners and/or 
operators of existing deep (Class I) underground injection wells that 
inject domestic wastewater effluent in specific counties in Florida. 
The counties are: Brevard, Broward, Charlotte, Collier, Dade, Flagler, 
Glades, Hendry, Highlands, Hillsborough, Indian River, Lee, Manatee, 
Martin, Monroe, Okeechobee, Orange, Osceola, Palm Beach, Pinellas, St. 
Johns, St. Lucie, Sarasota, and Volusia. Regulated categories and 
entities include:

------------------------------------------------------------------------
                Category                       Examples of entities
------------------------------------------------------------------------
Municipalities and Local Government....  Class I municipal injection
                                          wells disposing of domestic
                                          wastewater effluent in certain
                                          parts of Florida.
Private................................  Class I municipal injection
                                          wells disposing of domestic
                                          wastewater effluent in certain
                                          parts of Florida.
------------------------------------------------------------------------

    This table is not intended to be exhaustive, but rather provides a 
guide for readers regarding entities likely to be interested in this 
notice. This table lists the types of entities that EPA is now aware of 
that could potentially be affected by decisions related to this notice. 
Other types of entities could potentially be affected by such 
decisions. To determine whether your injection well might be affected, 
you should carefully examine the applicability criteria in 40 CFR 
146.15 of the July 7, 2000, proposed revisions to the Class I UIC 
regulations (65 FR 42234). If you have questions regarding the 
applicability of this action to a particular entity, consult one of the 
persons listed in the preceding FOR FURTHER INFORMATION CONTACT 
section.

II. Background

A. Definition of Class I Municipal Wells

    Class I injection wells are wells that inject fluids beneath the 
lowermost formation containing, within one-quarter mile of a well bore, 
a USDW (40 CFR 144.6(a)). Class I wells can be used to inject 
hazardous, industrial, or municipal wastes. Class I municipal wells 
inject treated wastewater from publicly or privately owned and operated 
facilities that treat domestic wastewater, which is principally derived 
from dwellings, business buildings, and institutions. Domestic 
wastewater is commonly referred to as sanitary wastewater or sewage. 
Treated wastewater from industrial facilities, often controlled through 
pretreatment standards, may also be found in this wastewater. 
Currently, Class I municipal wells are located only in the State of 
Florida.

B. Proposed Rule for Class I Municipal Wells in Florida

    EPA has established minimum requirements for Class I municipal 
wells and other underground injection activities through a series of 
UIC regulations at 40 CFR parts 144 through 147, developed under the 
authority of the Safe Drinking Water Act. These regulations ensure that 
Class I municipal wells will not endanger USDWs by prohibiting the 
movement of any contaminant into USDWs.
    On July 7, 2000, EPA proposed revisions to the UIC regulations that 
would allow continued wastewater injection by existing Class I 
municipal

[[Page 23675]]

wells that have caused or may cause movement of contaminants into USDWs 
in specific areas of Florida (65 FR 42234). Continued injection would 
be allowed only if owners or operators meet certain requirements that 
provide adequate protection for USDWs. In the alternative, if new 
requirements are not promulgated, owners and/or operators of wells 
targeted by the proposal would be required to close their wells and 
adopt different wastewater disposal practices, which could consist of 
surface water disposal, ocean outfall, and/or reuse. Use of these 
alternative disposal practices would likely require the construction of 
systems for advanced wastewater treatment, nutrient removal, and high-
level disinfection.
    The preamble to the proposed rule describes in detail the history 
of domestic wastewater injection in Florida, the features of Florida 
geology that have allowed some of that injected wastewater to enter 
USDWs, and the two major (as well as subsidiary) regulatory options EPA 
proposed to address this issue in a manner that would permit continued 
injection that would not endanger USDWs. EPA received approximately 
1,200 comments on the proposal (the comment period closed on October 
22, 2000). The Agency will address these comments, along with comments 
received in response to the related notice published separately in 
today's Federal Register, as part of the final determination on this 
rulemaking.

C. Relative Risk Assessment of Management Options for Treated Municipal 
Wastewater in South Florida

    As part of EPA's Fiscal Year 2000 Appropriations bill, Congress 
included the following provision: ``Within available funds, the 
conferees direct EPA to conduct a relative risk assessment of deep well 
injection, ocean disposal, surface discharge, and aquifer recharge of 
treated effluent in South Florida, in close cooperation with the 
Florida Department of Environmental Protection [DEP] and South Florida 
municipal water utilities.'' Because this directive came at a time when 
EPA's work on the July 7, 2000, proposal was substantially complete, 
the Agency decided to proceed with the proposal and the relative risk 
assessment along separate but converging paths. First, EPA published 
and sought comment on the proposal based on information available at 
that time. Second, EPA initiated and conducted the relative risk 
assessment with the intent of using relevant findings to inform the 
final rulemaking.
    EPA started the relative risk assessment by working with 
stakeholders to develop an appropriate methodology. The Agency first 
outlined a proposed methodology following standard risk assessment 
principles and guidance, such as the ``Guide for Developing Conceptual 
Models for Ecological Risk Assessments.'' \1\ EPA then held a 
stakeholders meeting on March 20, 2001, in Tallahassee, Florida to 
discuss the proposed methodology. The meeting was attended by 17 
stakeholders representing municipal water utilities, regulators, and 
community and environmental groups. Participants offered comments on 
the proposed methodology, which EPA revised accordingly.
---------------------------------------------------------------------------

    \1\ Prepared by G.W. Suter II of Oak Ridge National Laboratory 
for the U.S. Department of Energy. Report No. ES/ER/TM-186 issued in 
May 1996. Available at http://www.esd.ornl.gov/programs/ecorisk/tm186.pdf.
---------------------------------------------------------------------------

    The methodology involved a process for investigating the four very 
different wastewater disposal options: deep well injection, aquifer 
recharge, discharge to ocean outfalls, and discharge to other (non-
ocean) surface water bodies. Each option has its own specific stressors 
(hazards), exposure pathways, receptors, and effects. Parameters that 
are relevant to one particular disposal option are not necessarily 
relevant to the remaining three. Therefore, a strictly quantitative 
comparison between the four options was not possible.
    Instead, EPA conducted what is termed a relative risk assessment to 
assess the risks and allow comparisons. Individual risk assessments 
were completed for each wastewater disposal option and the risks 
associated with each were characterized. The risks and risk factors 
identified for each wastewater management option were then evaluated 
and described. The overall comparisons and conclusions were then 
presented as relative risk assessment matrices.
    The steps involved in the relative risk assessment included 
developing a Generic Risk Analysis Framework followed by conducting 
analyses of option-specific conceptual models. Data from many sources 
were used to support the analyses. These sources include the Florida 
Department of Environmental Protection, utilities (and the South 
Florida Water Environment Utility Council), and municipalities in South 
Florida. EPA also worked with a panel of experts both inside and 
outside of EPA and representing a variety of fields to review and 
incorporate data and information acquired through comprehensive 
searches of the relevant scientific research literature. Risk 
characterization for each option included identifying and describing 
the associated risks, their potential magnitude, and the potential 
effects on human and ecological health. The relative risk assessment 
then described and compared risks for all four wastewater management 
options. Finally, the relative risk assessment was peer reviewed in 
accordance with the Agency's Peer Review Handbook.
    Section III summarizes the major findings of the relative risk 
assessment, which has been finalized. In a separate notice of data 
availability published elsewhere in today's Federal Register, EPA 
requests comment on how the relative risk assessment should inform the 
final rulemaking on deep municipal injection wells in Florida.

III. Findings of the Relative Risk Assessment

    The relative risk assessment offers comparisons of deep well 
injection, ocean disposal, surface discharge, and aquifer recharge of 
treated municipal wastewater in South Florida by considering several 
factors important for determining risk. This section highlights how the 
report addresses the following questions: (A) What level of treatment 
and disinfection is provided? (B) What stressors remain (after 
treatment) that may be a concern? (C) What exposure pathways are (or 
may be) of significance? (D) What is the overall estimate of risk? (E) 
What are the important data or knowledge gaps? The purpose of this 
summary, the publication of the report, and this notice of availability 
is to discharge fully EPA's responsibility to complete the relative 
risk assessment mandated by Congress.

A. What Level of Treatment and Disinfection Is Provided?

    Municipal wastewater managed by any of the four options studied in 
South Florida receives secondary treatment, at a minimum. Secondary 
treatment comprises biological removal of dissolved organic and 
inorganic matter, commonly through such methods as activated sludge and 
trickling filter processes. By itself, secondary treatment does not 
provide disinfection, i.e., removal of microorganisms.
1. Deep Well Injection
    All facilities that manage municipal wastewater by deep well 
injection in Florida are required by Florida law to provide at least 
secondary treatment of the wastewater prior to injection. In addition, 
utilities that employ deep well injection must maintain disinfection 
capability, but many do not disinfect treated effluent prior to 
injection. For

[[Page 23676]]

example, treatment of wastewater that is injected by Class I municipal 
wells in Dade and Brevard Counties consists of secondary treatment with 
no disinfection, although backup disinfection capability is required. 
In contrast, in Pinellas County, wastewater is treated to more 
stringent reclaimed water standards before being discharged into Class 
I municipal wells, because the Class I wells are used to dispose of 
reclaimed water during periods of wet weather. Reclaimed water 
standards, as specified by the State of Florida, include secondary 
treatment plus a variety of techniques to remove microorganisms, 
including basic disinfection, filtration, and high-level disinfection.
2. Ocean Disposal
    Utilities in South Florida that employ ocean disposal provide basic 
disinfection in addition to secondary treatment prior to discharge. 
Basic disinfection removes fecal coliform bacteria by treating the 
wastewater with chlorine. However, wastewater that is discharged into 
the ocean does not undergo filtration. This means that pathogenic 
protozoans, such as Cryptosporidium, Giardia, and other chlorine-
resistant microorganisms, may remain in the treated wastewater.
3. Aquifer Recharge
    Utilities that employ aquifer recharge (which includes but is not 
limited to replenishment of surficial aquifers through irrigation, 
wetlands discharge, or discharge to percolation ponds) treat to 
reclaimed water standards prior to discharge. Small amounts of nitrogen 
and phosphorus and trace amounts of other inorganic and organic 
constituents remain. However, viruses and bacteria are inactivated and 
Cryptosporidium and Giardia are largely removed through filtration.
4. Surface Discharge
    Utilities in South Florida that employ surface water discharges 
provide advanced treatment as required to meet State water quality-
based effluent limits. Advanced wastewater treatment includes secondary 
treatment, basic disinfection, filtration, high-level disinfection, 
removal of chlorine following disinfection (i.e., dechlorination), and 
further removal of nitrogen and phosphorus. It represents the highest 
level of treatment conducted in South Florida.

B. What Stressors Remain (After Treatment) That May Be a Concern?

    ``Stressors'' include chemical or biological agents that may cause 
adverse effects if exposure levels are high enough. The relative risk 
assessment report describes the human health and ecological health 
stressors that may be found in wastewater effluent after it has been 
treated and that may pose a risk.

C. What Exposure Pathways Are (or May Be) of Significance?

    An ``exposure pathway'' is the course a stressor takes from a 
source of release to an exposed organism. It is defined by the 
different environmental media through which a stressor migrates (e.g., 
air, surface water, ground water) as well as the mechanism by which an 
organism is actually exposed (e.g., inhalation, drinking, topical 
contact). The relative risk assessment report discusses a variety of 
exposure pathways by which humans, plants, and animals may be exposed 
to municipal wastewater contaminants under each of the management 
options.

D. What Is the Overall Estimate of Risk?

    Although the report does not quantify risks, it offers conclusions 
about the relative risks of the four wastewater management options and 
about the various factors that influence risks to human and ecological 
health.
1. Human Health
    The human health risks associated with all four management options 
in South Florida are generally low. While it is difficult to compare 
the overall risks of the options directly, a relative comparison can be 
made on the basis of certain factors that tend to increase or decrease 
the risks of one or more options relative to the others. In particular, 
as discussed in turn in the following paragraphs, relative human health 
risks are higher when: (1) An option provides less wastewater 
treatment; (2) is more likely to contaminate current or potential 
drinking supplies; and (3) is more likely to result in people being 
exposed to discharged contaminants in other ways besides drinking.
    The degree of wastewater treatment, and in particular the level of 
disinfection and filtration of pathogenic microorganisms 
(Cryptosporidium, Giardia), is a major risk driver. Clearly, there is 
greater potential risks associated with wastewater that is not treated 
to remove microorganisms. This would suggest higher relative risks for 
the deep well injection and ocean disposal options, which generally do 
not filter wastewater to remove Cryptosporidium and Giardia prior to 
disposal. Looking just at deep well injection, the risk would be 
highest in situations where the injectate migrates through fractures, 
faults, and solution cavities. The risk associated with Cryptosporidium 
and Giardia being released by deep well injection would be mitigated 
somewhat in situations where the injection is dominated by porous media 
flow, characterized by long travel times to current or potential 
drinking water sources and fine pore spaces capable of retaining 
microorganisms.
    Once Cryptosporidium, Giardia, and other stressors are released to 
the environment, the level of risk they pose to human health depends 
largely on how likely they are to enter drinking water supplies. The 
relative risk assessment again suggests that deep well injection has a 
higher risk than the other options based on this factor. Movement of 
contamination into USDWs has been confirmed or is suspected at 9 of the 
45 municipal facilities that utilize Class I deep injection in South 
Florida, as evidenced by levels of nitrates and ammonia, as well as 
significant changes in dissolved solids concentrations. The other 
option with a relatively high risk of contaminating drinking water 
supplies is aquifer recharge. Ocean outfalls and surface water 
discharges pose a lower risk of contaminating drinking water supplies, 
for reasons given previously.
    Relative to the other options, however, ocean outfalls and surface 
water discharges pose a higher risk of people coming into direct 
contact with the released contaminants in other ways, such as by eating 
contaminated fish, by swimming in contaminated waters, and by 
participating in other recreational activities. These same two options 
also pose a risk of stimulating algal blooms that could be harmful, 
although this risk associated with surface water discharges is 
mitigated substantially by the removal of wastewater nutrients prior to 
release to surface waters in South Florida.
2. Ecological Health
    Overall, the risk to surface water ecosystems is low when treated 
wastewater is managed by deep well injection and aquifer recharge in 
South Florida. The risk to surface water ecosystems is also generally 
low when treated wastewater is discharged directly to surface waters. 
For all three of these management options, however, the potential for 
damage may be higher where treated wastewater is released in proximity 
to surface water that already has impaired water quality, which is the 
case for many surface water bodies in South Florida. In these cases, 
the nutrients that might enter impaired waters could exacerbate 
existing water quality and ecological problems.

[[Page 23677]]

    The risk to marine ecosystems is obviously greatest for the ocean 
disposal option. Ocean outfall monitoring data from available studies 
indicate that, for the most part, water quality standards are met by 
most constituents at the edge of the permitted mixing zone 
(approximated by a circle with a 400-meter radius), with the occasional 
exception of nitrogen and some metals. It is recognized, however, that 
effluent plumes may well extend outside the 400-meter radius and that 
marine organisms exposed in and around such plumes can likewise travel 
farther distances. Pathogenic microorganisms in particular pose some 
concern, because effluent discharged to the ocean is not filtered and 
there is some evidence to suggest that aquatic organisms suffer from 
high concentrations of such microorganisms. The effects of pathogenic 
microorganisms on aquatic animals need to be better documented, as does 
their concentration in ocean discharges and resulting plumes.
    Deep well injection could also pose a risk to marine ecology if 
contaminants can readily migrate and discharge to offshore waters. 
However, the extent to which this actually happens in South Florida and 
poses a real threat in the ocean is uncertain.
    Two potential ecological effects of particular concern, should 
surface or ocean waters be sufficiently contaminated, include harmful 
algal blooms and bioconcentration of toxic contaminants in the food 
web. Algal blooms can cause a variety of toxic symptoms in aquatic 
organisms (including death) as well as nontoxic adverse effects such as 
clogging of gills and smothering of coral reefs and seagrass beds. Food 
web bioconcentration of metals and other contaminants can also cause of 
variety of toxic effects.
    Finally, the ocean discharge option introduces the potential for 
the physical destruction of coral reefs traversed by discharge 
pipelines. The existing ocean outfalls in South Florida range from 0.9 
to 3.6 miles offshore. Any widening or extension of existing pipelines 
leading to these outfalls could impair or destroy any nearby coral 
reefs. The same would be true if new outfalls and pipelines are 
constructed through coral reefs in the future to accommodate increased 
disposal needs.

E. What Are the Important Data or Knowledge Gaps?

    For all four wastewater management options, the relative risk 
assessment found that there is a lack of definitive studies in South 
Florida that use a physical or chemical tracer or indicator to identify 
the source and transport pathways of stressors detected in the 
environment. Ocean discharge is the only disposal option for which 
there is a known tracer study proving the source of stressors. In this 
study, a stable isotope tracer indicated that nitrogen was not being 
taken up in any significant amount by phytoplankton in the vicinity of 
the South Florida ocean outfalls. However, without more definitive 
tracer studies for each wastewater management option, it is difficult 
to assess the potential effects of local conditions on the fate and 
transport of treated wastewater after being released into the 
environment.
    While results from ground water monitoring around some Class I 
municipal wells in South Florida confirm that fluids have migrated out 
of the permitted injection zone, the full areal extent of USDW impact 
is not known. This is not only because available monitoring data are 
limited, but also because the location and connectivity of natural 
conduits for fluid flow (fractures and solution cavities in the 
underground formation) are difficult to predict.
    Specifically for the deep well injection and aquifer recharge 
options, the fate and transport of pathogens in South Florida's 
aquifers are not completely understood. For example, the rates of 
microbial survival, inactivation, and transport are difficult to 
predict. Also uncertain are the rates of microbial straining or 
filtration by geological materials under different fluid flow 
scenarios, including porous media and conduit flow. The fate and 
transport of pathogens is especially difficult to verify for deep well 
injection, even with the most sophisticated modeling or with expensive 
monitoring, since the receiving formations are thousands of feet 
underground.
    Of particular relevance for the ocean disposal option, there is a 
lack of understanding regarding down-current impacts, risks to marine 
organisms passing through the mixing zone, and the potential for food 
web bioconcentration. Potential long-term ecological risks may exist 
inside and outside the mixing zone, but due to a lack of ongoing 
ecological monitoring studies around any of the existing ocean outfalls 
in South Florida, there is no information on actual biological 
receptors or exposure pathways that undoubtedly exist at the outfall 
sites. The lack of such long-term monitoring information makes it 
impossible to confirm that there are no long-term or cumulative 
ecological or biological effects of discharged effluent.
    With respect to surface discharges, there is significant 
uncertainty regarding the potential for food web bioconcentration and 
the severity of cumulative impacts caused by other sources of the same 
chemical and microbiological stressors contained in treated municipal 
wastewater.
    These other sources of contamination include onsite sewage disposal 
systems, non-point source runoff from agricultural or urban areas, 
atmospheric deposition, or other point sources. The risks posed by 
surface water discharge need to be put into overall context of the 
cumulative risks posed by all sources of stressors in order to gain a 
sense of their relative importance.

    Dated: April 17, 2003.
G. Tracy Mehan III,
Assistant Administrator for Water.
[FR Doc. 03-10269 Filed 5-2-03; 8:45 am]
BILLING CODE 6560-50-P